1. Field of the Invention
The present invention relates to an image forming apparatus.
2. Description of the Related Art
Japanese Patent Laid-Open No. 2008-126530 discloses an image forming apparatus that forms images on both sides of a long continuous roll sheet by an inkjet system. This apparatus acquires an image of the leading edge of a sheet supplied from a sheet supply unit and determines the print positions of a plurality of subsequent images with reference to the position information thereof. The continuous sheet whose first side is printed with the plurality of images is wound in a roll, and the trailing edge at the rear of the last image printed on the first side is cut. For second-side printing, the continuous sheet is drawn out from the wound roll and is fed to a recording unit, with the cut trailing edge at the head, at which a plurality of images are printed on the second side. If there is misalignment in the sheet conveying direction between the first side and the second side when the register marks thereof are visually checked, misalignment between images on the first side and images on the second side is corrected by inputting a length for correcting the misalignment from a terminal unit to thereby correct the image recording positions.
With the configuration disclosed in Japanese Patent Laid-Open No. 2008-126530, since a plurality of images can be printed on both sides of a continuous sheet without stopping, print processing efficiency is enhanced; however, little consideration is taken to consistency in image formation on the first side and the second side, with the print quality of both sides maintained. For example, if printed sheets subjected to duplex printing are bound into a book, such as a photobook, the sheets subjected to duplex printing serve as pages that constitute the book. Thus, it is important to control processes, such as maintenance printing for maintaining image quality, to prevent the image quality from differing between pages next to each other on the front and back. Furthermore, in an apparatus configured to achieve duplex printing by printing a first side and then printing a second side, if images cannot be printed on the second side in an intended manner, the page needs to be printed again, and the sheet whose first side is printed is wasted.